I bought some rock from TBS and it is loaded with crabs so I have actually become quite good at giving a good guess as I seem to hunt crabs and search IDs constantly as mine grow. From that picture the claw looks to have more of a blunt end than a terminal pincher. That is usually the sign of a crab that isn't inherently predatory. I would like to get a better picture of the side of the claw. Fat, tipped claws are only good for one thing, chaos. The blunt, skinny claws of the Mithrax are more for picking at rock for food. I have read 100s of stories, but have yet to have a bad Mithax crab. Mithax crabs seem to have bigger balls about being seen, the bad ones will usually hide quickly when they see you.